From Urban Terrain Models to Visible Cities

We are now faced with the possibility and in some cases the results of acquiring accurate digital representations of our cities. But these cities will not be capable of interactive visualization unless we meet some fundamental challenges. The first challenge is to take data from multiple sources, which are often accurate in themselves but incomplete, and weave them together into comprehensive models. Because of the size and extent of the data that can now be obtained, this modeling task is daunting and must be accomplished in a semi-automated manner. Once we have comprehensive models, and especially if we can build them rapidly and extend them at will, the next question is what to do with them. Thus the second challenge is to make the models visible. In particular they must be made interactively visible so they can be explored, inspected, and analyzed. In this article, we discuss the nature of the acquired urban data and how we are beginning to meet the challenges and produce visually navigable models. These models provide the basis for building virtual environments for a variety of applications

Side-looking radar in urban research - A case study

Capabilities of side-looking radar in urban researc

War on scale : models for the First World War battlefront

This essay traces the evolution and use of military scale models during the First World War. The application of such models by all belligerents is characterized by an enormous diversity in scale, context, construction method and purpose. Between the two extremes of a full scale replica of the Paris agglomeration and the tiny boxed miniature of a POW prison cell, a whole range of military models can be distinguished. On one hand, the model production can be considered part of a long tradition of military terrain modeling, as is evident in the examples of relief maps and training models. On the other hand, the rapidly changing technological and tactical developments during the Great War –such as strategic aerial bombing, camouflage and submarine warfare—require the creation of new types of scale models. During the last stages of the war, the encapsulation of the model as research object in a laboratory, looked at through optical devices and studied through model photography, demonstrates how this technological progress paves the way for a scientific approach towards warfare. The evolution of the models thus illustrates how war was waged on a variety of scales and that its theatre was far from limited to the battlefield itself

Airborne photogrammetry and LIDAR for DSM extraction and 3D change detection over an urban area : a comparative study

A digital surface model (DSM) extracted from stereoscopic aerial images, acquired in March 2000, is compared with a DSM derived from airborne light detection and ranging (lidar) data collected in July 2009. Three densely built-up study areas in the city centre of Ghent, Belgium, are selected, each covering approximately 0.4 km(2). The surface models, generated from the two different 3D acquisition methods, are compared qualitatively and quantitatively as to what extent they are suitable in modelling an urban environment, in particular for the 3D reconstruction of buildings. Then the data sets, which are acquired at two different epochs t(1) and t(2), are investigated as to what extent 3D (building) changes can be detected and modelled over the time interval. A difference model, generated by pixel-wise subtracting of both DSMs, indicates changes in elevation. Filters are proposed to differentiate 'real' building changes from false alarms provoked by model noise, outliers, vegetation, etc. A final 3D building change model maps all destructed and newly constructed buildings within the time interval t(2) - t(1). Based on the change model, the surface and volume of the building changes can be quantified

Global climate change and solutions for urban sustainability of Ho CHi Minh City, Vietnam

Ho Chi Minh City (HCMC), the largest city in Vietnam, is steadily growing, certainly towards a mega city in the near future. Like other mega cities at the boom stage, it has to face with serious environmental matters insolvable for many years. The situation may be worse under the effects of global climate change, geological subsidence due to non-standard construction and sea level rise. The situation of HCMC can be damaged or even broken by resonant effects of unsolved environmental matters and latent impacts of climate change. This article shows the challenges to the urban sustainable development under the duo effect of urban environmental matters and climate change in Ho Chi Minh City. Opportunities and strategic directions to overcome the challenges are also analyzed and recommended

Data visualization within urban models

Models of urban environments have many uses for town planning, pre-visualization of new building work and utility service planning. Many of these models are three-dimensional, and increasingly there is a move towards real-time presentation of such large models. In this paper we present an algorithm for generating consistent 3D models from a combination of data sources, including Ordnance Survey ground plans, aerial photography and laser height data. Although there have been several demonstrations of automatic generation of building models from 2D vector map data, in this paper we present a very robust solution that generates models that are suitable for real-time presentation. We then demonstrate a novel pollution visualization that uses these models

Introduction: Urban revolutions in the age of global urbanism

This special issue, papers presented at an Urban Studies Foundation-funded conference in Jakarta (March 2011), examines the current ‘urban century’ in terms of three revolutions. Revolutions from above index the logics and norms of mainstream global urbanism, particularly the form they have taken as policymakers work with municipal officials worldwide to organise urban development around neoliberal norms. Revolutions from below refer to the multifaceted contestations of global urbanism that take place in and around cities, ranging from urban street demonstrations and occupations (such as those riveting the world in early 2011 when these papers were written) to the quotidian actions of those pursuing politics and livelihoods that subvert the norms of mainstream global urbanism. It also highlights conceptual revolutions, referencing the ongoing challenge of reconceptualising urban theory from the South – not simply as a hemispheric location or geopolitical category but an epistemological stance, staged from many different locations but always fraught with the differentials of power and the weight of historical geographies. Drawing on the insights of scholars writing from, and not just about, such locations, a further iteration in this ‘southern’ turn of urban theorising is proposed. This spatio-temporal conjunctural approach emphasises how the specificity of cities – their existence as entities that are at once singular and universal – emerges from spatio-temporal dynamics, connectivities and horizontal and vertical relations. Practically, such scholarship entails taking the field seriously through collaborative work that is multi-sited, engages people along the spectrum of academics and activists, and is presented before and scrutinised by multiple publics

Numerical study of the urban geometrical representation impact in a surface energy budget model

The aim of this work is to investigate how both the orientation of the urban canyon and the modeling of the edge effects (i.e. urban canyons of finite length) are important in the numerical simulation of the surface energy budget in urban areas. Starting from the town energy balance scheme, two models of increasing complexity of the canyon geometry are developed. A sensitivity analysis of the role played by the chosen hypothesis and parameterizations is performed by coupling the canyon schemes with the numerical weather prediction model RAMS. The results suggest that a detailed description of the urban geometry could produce non-negligible differences of the energy balances and of the temperature fields with respect to what occurs using simpler schematizations, in particular during the summer